The invention pertains to a process for the manufacture of haloalkanes, or more particularly to a process for the manufacture of 1,1,1,3,3-pentachloropropane (HCC-240fa) and/or 1,1,1,3-tetrachloropropane (HCC-250fb).
Addition reactions for preparing useful haloalkanes, such as 1,1,1,3,3-pentachloropropane (HCC-240fa), are known in the art. Typically, in this reaction, a halogenated compound, such as carbon tetrachloride, is added to an olefinic compound, such as vinyl chloride monomer (VCM), in the presence of a catalyst and under conditions sufficient to form a haloalkane product having a backbone longer than that of the haloalkane reactant. The halogenated product then is recovered by separating it from the reactants, catalyst and by-products using conventional techniques such as distillation.
Although widely used, this process suffers from several shortcomings, one of the more serious being that the process is not readily adapted to continuous operation. The problem is due, in large part, to the recovery of the halogenated product from the product stream. Often such recovery destroys the catalyst, thereby eliminating the ability to recycle the catalyst. For example, Kotota et al. “Addition of Tetrachloromethane to Halogenated Ethenes Catalyzed by Transition Metal Complexes”, 77 J. Molec. Catal., 51-60 (1992), discloses a batch process for the preparation of HCC-240fa from carbon tetrachloride and vinyl chloride using as a catalyst, cuprous salts, cuprous chloride and Cu[(CH3—CN)4]Cl04, complexed with a co-catalyst, namely, n-butylamine. To recover the halogenated product, the catalyst and co-catalyst are removed by a water wash which destroys the catalyst. Since the catalyst is destroyed, it cannot be recycled. Reusing catalyst, however, is important to a commercially-viable, continuous process.
Other recovery processes disrupt the preparation process, thereby complicating a continuous process or frustrating it altogether. For example, in conventional processes, where recovery is effected by distilling a product stream to separate the haloalkane from the reactants and catalyst, the more volatile co-catalysts tend to flash off thus leaving a solid catalyst in the distillation column. Eventually, the process must be interrupted and the catalyst removed from the column, filtered, and physically transported to another vessel where it is mixed with the co-catalyst and introduced back to the reaction. In addition to disrupting the process, these recovery steps add cost and complexity to the reaction process.
Aside from the shortcomings related to recovering the haloalkane product, conventional addition reactions tend to have low selectivities. For example, Kotora et al., “Selective Additional of Polyhalogenated Compounds to Chlorosubstituted Ethenes Catalyzed by a Copper Complex,” React. Kinet. Catal. Lett., 415-19 (1991) discloses batch preparation of HCC-240 from carbon tetrachloride and vinyl chloride using a cuprous chloride complex catalyst with 2-propylamine as a co-catalyst. The reported HCC-240 yield, however, is only 71%.Additionally, Zhiryukina et al. “Synthesis of Polychloroalkanes With Several Different Chlorine-Containing Groups,” 1 Izv. Akad. Nauk SSR, Ser. Khim. 15257 (1983) also disclose a batch process for preparing HCC-240 from carbon tetrachloride and vinyl chloride using a Fe(CO)5-ethanol catalyst, which process reportedly yields 25% HCC-240. All of the above-disclosed processes are disadvantageous in that they are batch processes of low productivity and they have low selectivity for HCC-240. The Zhiryukina et al. process is further disadvantageous because it uses a highly toxic catalyst.
Therefore, a need exists for an efficient and economical continuous process for producing haloalkanes such as HCC-240fa in high yield. Further, HCC-240fa is a commercial raw material for the manufacture of HFC-245fa, and a need exists to develop alternative technologies to manufacture this material. The present invention addresses these needs, among others. Particularly, the present invention relates to new catalyst and co-catalyst systems, and to a new concept of dissolving a catalyst and co-catalyst in one of the reactants, e.g. CCl4, to form a homogeneous mixture. Subsequently, this mixture is fed to a reaction zone along with another reactant, e.g. VCM, preferably in a solid-free reaction.